1. Field of the Invention
The present invention relates to a novel protein and fragment thereof which can be used as a tumor marker in the diagnosis of pancreatic cancer as well as a process for diagnosing pancreatic cancer with use of the marker.
2. Background Art
It is known that pancreatic cancer is a cancer which originates in pancreas, and 90% or more of the cancer is pancreatic duct adenocarcinoma originating in the exocrine cells, particularly the cells of the pancreatic duct, through which pancreatic juice is transferred. It is very difficult to find pancreatic cancer, because pancreas is surrounded by many organs such as stomach, duodenum, spleen, small intestine, large intestine, liver and gall bladder. On the other hand, pancreatic cancer tends to begin spreading to other organs at its initial stage and thus has an inclination of easy metastasis. Thus, it is essential for the therapy of pancreatic cancer to detect it at its early stage.
In general, tumor markers which enable the diagnosis of cancers by blood test are useful for detection of cancer at its early stage. The tumor markers of pancreatic cancer include, for example, CA19-9, CEA, Dupan-2, and the like. However, it is often difficult to detect pancreatic cancer at its early stage even with these tumor markers. Therefore, there is a demand on the development of novel tumor markers of pancreatic cancer.
Fibrinogen is a glycoprotein which is transferred by blood and consists of three different polypeptide chains. If blood vessel is damaged, fibrinogen is cleaved by thrombin to form fibrin as the main ingredient of clot. In addition, it is known that the cleaved products such as fibrinogen and fibrin are involved with cell adhesion and cell dispersion, exhibit blood vessel contracting activities and chemotactic activities, and also work as mitogenic factors for several cell types. Furthermore, it is known that the plasma concentration of fibrinogen is involved with the risk of coronary diseases (J. Thromb. Haemost. 4(10), 2204-2209, 2006). It is also known that the genetic mutation of α chain of fibrinogen (α-fibrinogen) is involved with disorders such as abnormal fibrinogenemia, fibrinogenopenia, afibrinogenemia and renal amyloidosis (Thromb. Haemost. 96(2), 231-232, 2006; Blood 80(8), 1972-1979, 1992).